A thin-film-transistor (TFT) liquid-crystal-display (LCD) panel can be used in various applications, such as a notebook computer, a desktop monitor, or LCD television set. A TFT LCD panel has a matrix of pixels arranged in rows and columns. The columns of the matrix are driven by an analog voltage to create luminescence.
The relationship between the column drive (CD) analog voltage and the luminescence of a pixel is nonlinear (the so called “gamma curve”) and during the manufacturing process, each panel may have slightly different gamma curve response. As the size of TFT LCD panels increases, this variance between CD analog voltage and pixel brightness becomes more of a concern.
To compensate for this well-known “gamma effect” phenomenon, and thus improve overall performance of a TFT LCD panel, a digital programmable gamma correction circuit is employed. The digital programmable gamma correction circuit provides a number of gamma corrected voltages (i.e. a proper fitted reference gamma curve) so the column drive (CD) can provide the “right” voltage to each pixel for the proper luminescence of pixels throughout the TFT LCD panel.
A digital programmable gamma correction circuit is typically implemented in an integrated circuit (IC) device. For a large panel TFT-LCD panel, a digital programmable gamma correction circuit may have digital programmable gamma buffers of fourteen (14) to twenty (20) channels. Each channel is separately programmable and accepts its own independent, programmable digital data from a standard Inter-IC (I2C) interface or series port interface (SPI). Typically, an eight-bit (8-bit) to ten-bit (10 bit) digital-to-analog converter (DAC) is required for each of the digital programmable gamma channels to convert the independent, programmable digital data input into a corresponding analog voltage for use in adjusting luminescence. Because of the IC implementation of a programmable gamma correction circuit, it is desirable to optimize the layout for the circuit, for example, by reducing the size of the chip.